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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '50b2548c40c59423a1fd28b0221bbc009236df6029db4b02bd1516f47f34c3b8' 
  AND token = '5AWqWQ812EvXER2Iw/dBtZsXd5tzcFssQF6eZAYbK48=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}